Starbucks helped increase the quality of coffee shops in most cities and in the case of Japan, I believe, it helped lower the price of a cup of coffee. There are 3 Starbucks shops within 90 seconds walk from my office. The market appears saturated but people sure drink a lot of coffee because there are other brands of shops within the said blocks as well.
By the way, there is one market where Starbucks is not able to penetrate and that is in French Canada because of their long tradition of good coffee shops. If existing coffee shops are good and competitive they need not fear Starbucks.